July 29th, 2014

F-TR Champ’s Secret Weapon — 40X Rimfire F-TR Trainer

2012 U.S. National F-TR Individual Champion James Crofts is one of America’s top F-Class shooters. A member of the 2013 World Championship-winning F-TR Team USA squad, James knows a thing or two about long-range shooting, that’s for sure. But you may be surprised to learn how James sharpens his shooting skills at relatively short distances. You see, James often practices with a .22 LR rimfire rifle at distances from 50 to 200 yards. James tells us: “Shooting my F-Class rimfire trainer saves me money and improves my shot process and wind-reading abilities.”

Remington rimfire 40X barreled action in PR&T LowBoy stock with PT&G bolt.
James Crofts F-TR Rimfire .22 LR

Rimfire Training Teaches Wind-Reading Skills by James Crofts
Training with the rimfire is extremely useful and can be done from 25 yards out to 200 yards. I am lucky and can shoot 50 yards right off my back deck. That is far enough that any miscue on rifle handling will show up on the target. I use a two dry-fire to one actual shot routine for my practices. This gives me much more positive reinforcement without any negative reinforcement.

Wind reading is extremely important with a .22 LR rifle. I use a set of smallbore flags to aid my wind calls. The smallbore flags are a must and force you to look at the flags and mirage on each and every shot. If you think the flags at Camp Butner move a lot, try smallbore flags around tall pine trees.

Rimfire Training Is Cost-Effective
Rimfire ammunition is much less costly than centerfire ammo. Though .22 LR prices have risen in recent years (and rimfire ammo is harder to find), even now I can get a 500-round brick of .22 LR ammo for less than $75.00. That works out to fifteen cents a round. That’s a fraction of the cost of handloading .308 Win match ammo. Heck, you can pay 40 cents a piece for match-grade .308-cal centerfire bullets. Then you have to figure in brass, primers, and powder.

James Crofts F-TR Rimfire .22 LR

My CMP 40X Rimfire F-TR LowBoy Clone
My quest into the .22 LLR rimfire field started with an email from the Civilian Marksmanship Program (CMP) announcing Rem 40X stripped barreled actions for sale. I thought, “Hmmm… Could one of those little 40X barreled actions be turned into a F-Class training rifle?” My gunsmith Ray Bowman of Precision Rifle & Tool was brought in at this point.

After conferring with Ray, it was decided that he could indeed turn this into a F-Class training rifle. Ray contacted Dave Kiff of PT&G and ordered a new bolt for the Remington 40X rimfire action. Next was the stock decision. I decided to go with a PR&T Low Boy F-Class stock — this is an exact clone of the stock for my .308 Win F-TR competition rifle. Then a Jewell trigger was acquired to complete the components. Ray built this just like he would any custom rifle, other than using the stock barrel. The project turned out awesome. The rifle was a hammer from the beginning even with the stock barrel.

James Crofts F-TR Rimfire .22 LR


About James Crofts
This spring, James Crofts was chosen as the new Vice Captain for the USA F-TR National Team. James comes from a military background, having served 20 years in the U.S. Navy aboard fast attack submarines. James has also been a shooting member of the 8-man F-TR Team USA, and he is always one of the top shooters in any F-TR competition. James told us: “Now the work begins, but with Ray Gross as Captain I think we can handle it. It will be a tough act to follow. Darrell Buell and Mike Miller set the bar extremely high with back-to-back world championship gold medals.”

James Crofts F-TR Rimfire .22 LR
James Crofts — Photo by Kent Reeve.

Permalink Competition, Gunsmithing Post comment »
July 29th, 2014

Nightforce Releases new 5-20x56mm SHV Scope

Nightforce now offers a 5-20x56mm SHV scope that retails for $1170.00 (non-illuminated) or $1299.00 (illuminated). This follows up on Nightforce’s successful 4-16x56mm SHV scope. The higher magnification range suits long range hunters and the large 56mm objective provides excellent low-light hunting capability. The 5-20 SHV offers plenty of travel: 80 MOA total elevation, 50 MOA windage.

Nightforce SHV MOAR reticle scope

The 5-20x56mm SHV boasts capped, waterproof turrets with 1/4-MOA click values, and 10 MOA per revolution on the elevation turret. The scope offers a side parallax control (25 yards to infinity), plus a European-style, fast-focus eyepiece.

Two reticles are offered for the 5-20x56mm SHV. The IHR features large dagger-style pointers, an open field at the top, and an cross in the center. The MOAR reticle has 1 MOA elevation and windage markings, with a floating center crosshair. With either reticle, illumination is optional at extra cost.

Nightforce SHV MOAR reticle scopeNightforce SHV MOAR reticle scope

Our friend Len Backus of LongRangeHunting.com has checked out the new 5-20x56mm Nightforce and he is impressed: “With a 56mm objective the SHV’s light transmission is outstanding even at high power. Nightforce has added a ‘Zero Set’ feature which is a set-screw based stop system allowing you to dial back to your pre-set zero and stopping you from dialing past. It’s not quite as sharp a stop as their ‘Zero Stop’ but it will definitely do the trick. I bought my first Nightforce scope about 14 years ago. In summer of 2012 I had a four-hour private tour of the Nightforce headquarters. I remember being so impressed with the forward thinking going on there. It was obvious they were preparing for a major push on new technology and new products and this SHV is an absolute winner in that regard.”

Product Tip from EdLongrange. We welcome reader submissions.
Permalink New Product, Optics Post comment »
July 29th, 2014

Canadian Website for Benchrest Shooters

Benchrest Canada

Did you know that, since 2009, Canada has had its own dedicated website for short-range benchrest: www.Benchrest.ca? Founder/webmaster Rick Pollock notes: “As Benchrest up here in the great white north has little or no web presence, a website was long overdue. It is non-commercial and not affiliated with any one sanctioning body. The only aim is to get more people into Benchrest in Canada.”

The site is a valuable resource. You’ll find upcoming BR matches (in Benchrest.ca online forum), a list of clubs, recent news, and, of course, match reports. In addition there is a buy/sell “classifieds ads” section, as well as a photo gallery. Benchrest.ca also has a YouTube Video Archive with clips showing many of the legends of the sport. Here’s a 2010 Benchrest.ca video showing Tony Boyer at the 2010 NBRSA Nationals:

If you live “North of the Border” and shoot benchrest for score and/or group, definitely visit (and bookmark) www.Benchrest.ca.

Benchrest Canada

Permalink News 2 Comments »
July 28th, 2014

High Power National Championship — The Guns of Camp Perry

We are already half-way through the NRA High Power National Championship and SSG Shane Barnhart of the USAMU remains atop the leaderboard, with a score of 1193-64X out of a possible 1200 points. Barnhart shot a 595-28X during Sunday’s Navy Cup, Coast Guard Trophy, and Army Cup matches. Barnhart currently holds a three-point lead over second place SSG Brandon Green (1190-58X), the defending High Power National Champion. Like Barnhart, Green shoots for the USAMU. Kenneth Lankford leads the “any sight” (scopes allowed) division with 1191-54X.

High Power Hardware: The Guns of Perry

We thought our readers would like to see some of the ultra-accurate rifles campaigned by High Power competitors at Camp Perry. Both bolt-action and self-loading rifles are popular. Among bolt guns, Tubb 2000s and Eliseo tubeguns are popular. Semi-auto AR platform “Space Guns” offer some advantages (particularly during rapid-fire and for standing position), and are favored by many of the top marksmen. Many Camp Perry High Power competitors are also shooting less exotic AR service rifles.

Here is your current leader, SSG Shane Barnhart, with an AR Space Gun. Note the side charging handle and tall iron sight set-up.
Camp Perry AR15 Tubegun High Power Space Gun Tubb 2000 Rifle Standing

Tubb 2000 with a shortened handguard, and custom hand support bracket forward of mag well.
Camp Perry AR15 Tubegun High Power Space Gun Tubb 2000 Rifle Standing

The modern AR Space Gun, scoped version. Note the side charging handle, and absence of forward assist. A block fitted under the handguard helps with the standing position. The scope is mounted on a “piggy-back” rail that extends forward of upper receiver’s built-in rail.
Camp Perry AR15 Tubegun High Power Space Gun Tubb 2000 Rifle Standing

Tubb 2000 rifle, left-hand version. Note how the butt-plate is adjusted for cant, angle, and drop.
Camp Perry AR15 Tubegun High Power Space Gun Tubb 2000 Rifle Standing

Look carefully — it appears that a separate fore-arm section is duct-taped to the red free-floated handguard. Perhaps this AR owner experienced some wiggle, and that’s why he seems puzzled?
Camp Perry AR15 Tubegun High Power Space Gun Tubb 2000 Rifle Standing

A countdown timer is attached directly to this shooter’s Tubb 2000 rifle.
Camp Perry AR15 Tubegun High Power Space Gun Tubb 2000 Rifle Standing

This Service Rifle competitor shows how to get some “R & R” between relays.
Camp Perry AR15 Tubegun High Power Space Gun Tubb 2000 Rifle Standing


All Photos courtesy NRA General Operations.

Permalink Competition, Gear Review 2 Comments »
July 28th, 2014

Remington Announces R51 Pistol Exchange

Maybe the “R” in Remington’s 9mm R51 pistol stands for “recall”, or more accurately “replacement”. Responding to many complaints from pistol buyers (and some embarrassing videos posted on YouTube), Remington has offered to exchange the pistols: “Anyone who purchased an R51 may return it and receive a new R51 pistol, along with two additional magazines and a custom Pelican case, by calling Remington at (800) 243-9700.” The second generation R51 pistols should be available by late October, according to Remington.

Remington R51 recall model 51

So, if your R51 is a lemon, you can get a new one, presumably one that is more reliable. It’s good that Remington is “doing the right thing” for its customers. But one wonders why Remington would sell a product that was clearly “not ready for prime time”. Apparently the early test pistols worked well, but production versions had problems. Remington has issued the following statement:

Remington R51 Exchange
Earlier this year, we launched the innovative R51 subcompact pistol to critical acclaim. During testing, numerous experts found the pistol to function flawlessly. In fact, they found it to have lower felt recoil, lower muzzle rise and better accuracy and concealability than other products in its class.

However, after initial commercial sales, our loyal customers notified us that some R51 pistols had performance issues.

We immediately ceased production to re-test the product. While we determined the pistols were safe, certain units did not meet Remington’s performance criteria. The performance problems resulted from complications during our transition from prototype to mass production. These problems have been identified and solutions are being implemented, with an expected production restart in October.

Anyone who purchased an R51 may return it and receive a new R51 pistol, along with two additional magazines and a custom Pelican case, by calling Remington at (800) 243-9700.

The Original Remington Model 51
The Remington R51 pistol is a much updated version of the Remington Model 51, a 1917-18 design by John D. Pedersen. The original Model 51 was chambered for .380 ACP, and later .32 ACP. It had a very low bore axis, made possible by the Pedersen’s “hesitation lock design”. The Model 51 pointed very naturally, and with its low bore axis, muzzle flip and perceived recoil was less than with other pistols of similar size, weight, and caliber.

Remington R51 recall model 51

Like a blowback pistol, the original Remington 51 has a stationary barrel and recoil spring surrounding the barrel. However, the Remington 51 employed a unique locking breech block within the slide. When the Model 51 is in battery, the breech block rests slightly forward of the locking shoulder in the frame. When the cartridge is fired, the bolt and slide move together a short distance rearward powered by the energy of the cartridge.

Remington R51 recall model 51

When the breech block contacts the locking shoulder, it stops, locking the breech. The slide continues rearward with the momentum it acquired in the initial phase. This allows chamber pressure to drop to safe levels while the breech is locked and the cartridge slightly extracted. Once the bullet leaves the barrel and pressure drops, the rearward motion of the slide lifts the breech block from its locking recess through a cam arrangement, continuing the operating cycle. The Remington Model 51 was the only production pistol to utilize Pedersen’s type of operating system. However a prototype .45 ACP version, the Remington Model 53, was built for testing by the Navy Board.

Permalink Handguns, News 3 Comments »
July 28th, 2014

Sinclair Product Report: Thumler’s Tumbler with Stainless Media

We know that many of our readers are now tumbling their brass in liquid media rather than dry media such as corn-cob or walnut shells. When done with STM stainless tumbling media (small ss pins), this system really does work, producing brass that is clean “inside and out”. The only down-side to wet tumbling is that sometimes the inside of the caseneck gets so “squeaky clean” that bullets take more effort to seat. This can be remedied with the use of a dry lube inside the necks. When cleaning with stainless tumbling media you’ll need a quality tumbler that is water-tight. The wet-tumbler of choice is the Model B Thumler’s Tumbler. Featuring a bright-red, side-loading drum, the Model B Thumler’s Tumbler is reliable and built to last.

A while back, Bill Gravatt, then President of Sinclair Int’l, had a chance to evaluate the Thumler’s Tumbler and the wet-cleaning process for cartridge brass. Bill came away a believer: “I wanted to share with you my experience using the Thumler’s Tumbler and stainless steel pin media to clean brass.

I used it for the first time just before the National Matches on some .308 Winchester brass. I just added water and some Simple Green All-Purpose Cleaner and tumbled them for about 45 to 60 minutes. Wow! I have never had cases so clean both inside and out. The tumbler I used was the sample from our photo studio, and someone had left a 223 Remington case in there that was completely tarnished dark green. I left it in to see what would happen, and it came out just as clean as my .308 cases.

A lot of customers, and a couple of our techs, have told me about the good results they get with this tumbler, but I was still very impressed. At Camp Perry, I talked to a few shooters who had used it, and they all had only good things to say about the Thumler system. Of course, being shooters, they all had their own concoctions (recipes) of various cleaners. All I can say is that the Simple Green worked well for me. If you want to try something different for cleaning brass, you might want to give the Thumler system a tryout. The great thing about the stainless steel media is that it never wears out. Buy it once and never buy media again. We sell a kit of the Tumbler and 5 lbs. of media that will save you a few bucks off buying them separately.” — Bill Gravatt

Permalink Reloading 5 Comments »
July 27th, 2014

Great Deals on Rimfire Guns at CDNN

Everyone needs a few good .22 LR firearms for fun shooting, target practice, and cross-training. We found two exceptional deals right now at CDNN Sports, a large wholesaler that specializes in inventory close-outs. CDNN acquires products at low cost, so they can sell well below MSRP.

The first item that caught our eye was a nice 1911-style target pistol. These full-size, German-made GSG rimfire 1911s often sell for $400.00 or more (MSRP is $427.95). This item is currently on sale for just $279.99. Plus a $30.00 distributor’s rebate is available for purchases made through July 31, 2014 (so you’ve got a few more days to grab one for $249.99 after rebate). Because the GSG is the same size as a centerfire 1911 pistol, the GSG is great for cross-training. The GSG is also compatible with many full-size 1911 parts.

GSG .22 LR Ruger 10/22 special

German Sport Guns (GSG) M1911 Target — Same Look And Feel As Full-Size M1911

GSG .22 LR Ruger 10/22 special

Ruger 10/22 with Synthetic Stock or Wood Stock for $189.99
If you own a ranch or farm, or have some kids (or grand-kids) who enjoy plinking, a Ruger 10/22 should be part of your gun collection. For 50 years, the Ruger 10/22 has been America’s favorite .22 LR rifle. Durable and simple, the Ruger® 10/22® rifle is well-suited for informal target shooting, “plinking”, and eradicating small varmints. And now you can get one for under $200.00.

GSG .22 LR Ruger 10/22 special

CDNN currently has the 10/22 with synthetic stock on sale for $189.99. Weighing just 5 pounds, this rifle features an 18.5″ barrel, 13.50″ Length Of Pull, and a 10-round rotary magazine. MSRP is MSRP $279.00, so this is a very good deal. A wood-stocked version is also offered for just $189.99.

GSG .22 LR Ruger 10/22 special

Permalink Hot Deals Post comment »
July 27th, 2014

Bastogne Beauty — F-Classer from Master Class Stocks

Alex Sitman Master Class StocksAlex Sitman of Master Class Stocks in Pennsylvania is widely considered one of the finest rifle-stock craftsmen in the country, if not the world. Alex’s workmanship and dedication to excellence is top-of-the-line. Alex normally custom-fits each stock to his customer precisely. Many hours are dedicated to stock prep and inletting, and his bedding jobs are flawless. Each stock is exactingly hand-crafted with great attention to detail, and then the stock is “dressed” in the customer’s choice of finishes.

Doing all that takes time — a lot of time. That’s why Master Class Stocks has a long waiting list, and it can take months before a big job is completed. But when Alex is involved, you can count on the final product being a work of stock-making art. Here’s an example. Alex recently stocked an F-Class rifle using eye-popping, exhibition-grade Bastogne walnut. The wood was sourced from Cecil Fredi of GunstockBlanks.com. Alex says: “Cecil’s wood is some of the best I’ve ever used. This blank cost over $1000.00, but it was truly spectacular.” Since the blank was less than 3″ wide, Alex (with assistance from 8-time NRA High Power Champion Carl Bernosky) laminated on the 3″-wide forearm “wings” using spare wood left after the blank was cut. See how Alex and Carl carefully matched the grain of the wood on the forearm. And note how perfectly the adjustable cheek-piece is fitted. If you want a stock like this on your next rifle, contact Alex Sitman at Master Class Stocks, (814) 742-7868.

The Bastogne Beauty — More Construction Details
Eric Kennard tells us: “This rifle was built for Mike Dana in Florida. Kelbly’s did the metal work. [The action is a Stolle Panda F-Class.] Barrel by Brux. Chambering? 6mmBR of course! Mike added a March 10 x 60 scope. Let me tell you this is beyond a work of art! The fit is absolutely perfect! There is not one flaw in the wood-work. The pillar bedding is also perfect! Did you notice the ebony inserts? Or Alex’s custom trigger guard? Alex out did-himself this time. Most of us would not dare to shoot [this gun]!”

Permalink Gunsmithing 9 Comments »
July 27th, 2014

Tech Tip: Always Check Headspace with New Barrels

A friend of ours recently took delivery of a new barrel which was chambered by a smith who had done the original build on the rifle, but who had not headspaced the barrel on the action itself this time. The smith headspaced based on his old records. Our friend happily screwed on his nice, new barrel and headed to the range. After the first few rounds, with known, safe loads, he was seeing deep craters on his primers, and then he even pierced a few primers with loads that should never have done that. Interestingly, the brass was not showing any of the other pressure signs. This was with bullets seated .015″ out of the rifling.

We were thinking maybe too much firing pin extrusion or maybe he got a hot lot of powder. Then I asked him to email me dimensions off his fired cases compared to new, Lapua brass. He emailed me that his shoulder moved 0.0105″ forward. I sent an email back saying, “hey, that must be a typo, you meant 0.0015″ right–so your shoulder moved one and a half thousandths correct?” The answer was “No, the shoulder moved over TEN thousandths forward”. Ahah. This explained some of the cratering problem in his brass. His cases were able to bounce forward enough in the chamber so that the primer material was smearing over the firing pin. And now he has brass that is “semi-improved”.

go no-go field headspace gauges

The point of the story is always check your headspace when you receive a “pre-fit” barrel, even from the smith who built the rifle. Purchase Go/No Go gauges for all your calibers. Headspace is not just an accuracy issue, it can be a safety issue. Pierced primers are bad news. The debris from the primer cup can blow into the firing pin hole or ejector recess causing a myriad of problems.

Permalink Gunsmithing, Tech Tip Post comment »
July 26th, 2014

SCATT MX-02 for High Power Shooters

The SCATT MX-02 is a revolutionary electronic shooter training system that is capable of operating outdoors with live, centerfire ammunition, at distances from 25 yards to 600 yards. Tony Chow recently tested this product, as fitted to his AR-15 Service Rifle. Tony concludes this is a very useful tool that can help High Power competitors refine their technique and thereby shoot higher scores. CLICK HERE for Full 3000-word Review.

SCATT MX-02 training digital camera sensor target

How the SCATT MX-02 Works
The SCATT sensor mounted on the end of the barrel has a digital camera that recognizes the black bullseye in the target, even in broad daylight outdoors. Using the bullseye as a reference, the SCATT software tracks the movement of the muzzle relative to the center of the target. The unit can plot these movements as a continuous trace, which appears on a monitor as a squiggly, colored line. By sensing the exact moment of shot release, the SCATT can also interpolate relative shot placement (for a single shot or series of shots) — but this is not the same as an electronic target which actually records the exact shot impact location on the target.

SCATT MX-02 training digital camera sensor target

Back in January, we reviewed this product from the perspective of a smallbore competitive shooter. (Read Previous Review.) Recently, we had the chance to test SCATT MX-02 again, this time on an AR-15 service rifle, in order to assess its implications for the High Power competition community.

We put the MX-02 through its paces in all three High Power shooting positions and in various environmental conditions. We wanted to find out whether the system can reliably operate in the harsher outdoor settings and withstand the recoil of a centerfire rifle. We also wanted to assess whether it provides added values for High Power shooters over older generation of electronic trainers such as SCATT’s own venerable WS-01.

On both counts, we came away impressed. The SCATT MX-02 stood up to centerfire recoil after hundreds of shots and was able to consistently recognize the often less-than-pristine High Power target faces. Both indoors and outdoors, the MX-02 acts as SCATT should and dutifully captures useful aiming traces and other data. It does that even during outdoor live-fire sessions, where shooter performance often differs from indoor dry-firing due to the sensation of recoil and environmental factors.

SCATT Rapid Fire Results (paper target on left, screen on right).
Scatt MX-02 shooting trainer camera

In particular, SCATT MX-02 allows shooters to effectively troubleshoot and improve their rapid-fire performance, a service that no previous-generation trainers are capable of providing. The unit isn’t perfect — the SCATT MX-02 had some mounting issues with small-diameter barrels, but a cardboard shim provided a quick and effective solution.

CLICK HERE for Full SCATT MX-02 Review.

Overall, performance was impressive. In most realistic training conditions that High Power shooters experience, the system performed well. We can certainly recommend SCATT MX-02 as an extremely valuable tool for High Power competitors looking to take their performance to the next level.

Test Drive the MX-02 at Camp Perry
SCATT electronic training systems are currently on display at the NRA National Championships in Camp Perry, Ohio. Interested shooters can try out SCATT at Champion Shooters on Commercial Row, Building #1023B.

For more information or to order SCATT products, including the new MX-02, visit ScattUSA.com or call toll-free: 1-855-57-SCATT (72288).

Permalink Gear Review, New Product Post comment »
July 26th, 2014

Jerry Miculek Shoots Original, Full-Auto AR-10 from the Fifties

Today, AR-platform rifles are hugely popular. Dozens of manufacturers sell AR-type rifles, in a wide variety of configurations and calibers. But before there were M16s and AR-15s, ArmaLite produced a 7.62×51 caliber rifle, the AR-10. Invented by Eugene (‘Gene’) Stoner for the Armalite company, this is the father of all of today’s AR-platform rifles.

If you’re curious about the AR-10, in this video, Jerry Miculek puts an original 1957-vintage AR-10 through its paces on the range. This extremely rare, early-production rifle was provided by Mr. Reed Knight and the Institute of Military Technology. (The gun in the video was actually produced in the Netherlands under license, see video at 4:40.) This AR-10 is the direct ancestor of the AR-15, M16, and many of the modern sporting rifles that we use today.

The AR-10 was slim and light, weighing in at around 7 pounds. Some folks might argue that the original “old-school” AR10 is actually better that some of today’s heavy, gadget-laden ARs. The AR-10′s charging “lever” was under the carry handle — that made it easier to manipulate with the gun raised in a firing position.

AR-10 Armalite Jerry Miculek

You’ll notice there is no “forward assist”. Inventor Gene Stoner did not believe a separate “bolt-pusher” was necessary. The forward assist was added to solve problems encountered in Viet Nam. Some critics say the forward assist “only takes a small problem and makes it a big problem.” For today’s competition ARs (that are never dragged through the mud) the forward assist probably is superfluous. It is rarely if ever needed.

AR-10 Armalite Jerry Miculek

Note also that the handguards are fairly slim and tapered. Today, six decades after the first AR-10 prototypes, we are now seeing these kind of slim handguards (made from aluminum or lightweight composites) used on “full race” ARs campaigned in 3-gun competition.

AR-10 Armalite Jerry Miculek

History of the AR-10
The AR-10 is a 7.62 mm battle rifle developed by Eugene Stoner in the late 1950s at ArmaLite, then a division of the Fairchild Aircraft Corporation. When first introduced in 1956, the AR-10 used an innovative straight-line barrel/stock design with phenolic composite and forged alloy parts resulting in a small arm significantly easier to control in automatic fire and over one pound lighter than other infantry rifles of the day. Over its production life, the original AR-10 was built in relatively small numbers, with fewer than 9,900 rifles assembled.

In 1957, the basic AR-10 design was substantially modified by ArmaLite to accommodate the .223 Remington cartridge, and given the designation AR-15. ArmaLite licensed the AR-10 and AR-15 designs to Colt Firearms. The AR-15 eventually became the M16 rifle.

AR-10 photos from Arms Izarra, a Spanish company specializing in de-militarized, collectible firearms. Interestingly, this particular AR-10 was produced in the Netherlands under license.

Permalink - Videos, Gunsmithing Post comment »
July 26th, 2014

Coefficient Conundrum: G1 vs. G7, Which BC Should You Use

The better, up-to-date ballistics programs let you select either G1 or G7 Ballistic Coefficient (BC) values when calculating a trajectory. The ballistic coefficient (BC) of a body is a measure of its ability to overcome air resistance in flight. You’ve probably seen that G7 values are numerically lower than G1 values for the same bullet (typically). But that doesn’t mean you should select a G1 value simply because it is higher.

Some readers are not quite sure about the difference between G1 and G7 models. One forum member wrote us: “I went on the JBM Ballistics website to use the web-based Trajectory Calculator and when I got to the part that gives you a choice to choose between G1 and G7 BC, I was stumped. What determines how, or which one to use?”

The simple answer to that is the G1 value normally works better for shorter flat-based bullets, while the G7 value should work better for longer, boat-tailed bullets.

G1 vs. G7 Ballistic Coefficients — Which Is Right for You?
G1 and G7 refer both refer to aerodynamic drag models based on particular “standard projectile” shapes. The G1 shape looks like a flat-based bullet. The G7 shape is quite different, and better approximates the geometry of a modern long-range bullet. So, when choosing your drag model, G1 is preferrable for flat-based bullets, while G7 is ordinarily a “better fit” for longer, boat-tailed bullets.

G1 G7 Ballistic coefficients

Drag Models — G7 is better than G1 for Long-Range Bullets
Many ballistics programs still offer only the default G1 drag model. Bryan Litz, author of Applied Ballistics for Long Range Shooting, believes the G7 standard is preferrable for long-range, low-drag bullets: “Part of the reason there is so much ‘slop’ in advertised BCs is because they’re referenced to the G1 standard which is very speed sensitive. The G7 standard is more appropriate for long range bullets. Here’s the results of my testing on two low-drag, long-range boat-tail bullets, so you can see how the G1 and G7 Ballistic coefficients compare:

G1 BCs, averaged between 1500 fps and 3000 fps:
Berger 180 VLD: 0.659 lb/in²
JLK 180: 0.645 lb/in²

The reason the BC for the JLK is less is mostly because the meplat was significantly larger on the particular lot that I tested (0.075″ vs 0.059″; see attached drawings).

For bullets like these, it’s much better to use the G7 standard. The following BCs are referenced to the G7 standard, and are constant for all speeds.

G7 BCs:
Berger 180 VLD: 0.337 lb/in²
JLK 180: 0.330 lb/in²

Many modern ballistics programs, including the free online JBM Ballistics Program, are able to use BCs referenced to G7 standards. When available, these BCs are more appropriate for long range bullets, according to Bryan.

[Editor's NOTE: BCs are normally reported simply as an 0.XXX number. The lb/in² tag applies to all BCs, but is commonly left off for simplicity.]

Permalink Bullets, Brass, Ammo Post comment »